Liquid electrophotographic printing, also referred to as liquid electrostatic printing, uses liquid toner to form images on a print medium. A liquid electrophotographic printer may use digitally controlled lasers to create a latent image in the charged surface of an imaging element such as a photo imaging plate. In this process, a uniform static electric charge is applied to the imaging element and the lasers dissipate charge in certain areas creating the latent image in the form of an invisible electrostatic charge pattern conforming to the image to be printed. An electrically charged printing substance, in the form of liquid toner, is then applied and attracted to the partially-charged surface of the imaging element, recreating the desired image.
In certain liquid electrophotographic printers, a transfer element is used to transfer developed liquid toner to a print medium. For example, a developed image, comprising liquid toner aligned according to a latent image, may be transferred from an imaging element to a transfer blanket of a heatable transfer cylinder and from the transfer blanket to a desired substrate, which is placed into contact with the transfer blanket.
At least two different methodologies may be used to print multi-color images on a liquid electrophotographic printer. Both methodologies involve the generation of multiple separations, where each separation is a single-color partial image. When these separations are superimposed they result in the desired full color image being formed. In a first methodology, a color separation layer is generated on the imaging element, transferred to the transfer cylinder and is finally transferred to a substrate. Subsequent color separation layers are similarly formed and are successively transferred to the substrate on top of the previous layer(s). This is sometimes known as a “multi-shot color” imaging sequence. In a second methodology, a “one shot color” process is used. In these systems, the imaging element transfers a succession of separations to the transfer blanket on the transfer cylinder, building up each separation layer on the blanket. Once some number of separations are formed on the transfer blanket, they are all transferred to the substrate together.